In a paging system, a mobile individual carries a portable pager. Typically, the pager is assigned a telephone number and is capable of receiving a predetermined radio signal. When a caller dials the pager's number the predetermined radio signal is broadcast and the pager responds to the signal by activating an audible and/or visual alarm. The alarm serves to alert the mobile individual that an attempt has been made to contact the mobile individual. Often, the caller's telephone number will be included in the radio signal so that the pager can record the caller's number and the called party can initiate a return call at some later time. One of the drawbacks of past paging systems is that they do not usually support two-way communication. Thus, in a typical paging scenario, the called party must relocate and initiate a return call to establish full two-way communication with the calling party. Such relocation may be inconvenient and untimely resulting in "telephone tag"--situations in which two individuals periodically try to contact one another and fail because the other person is unavailable.
Another drawback of past paging systems is the delay associated with the paging queue. In general, a paging service can only transmit one page at a time. However, a service usually receives many paging requests at once. Consequently, a queue builds up at the service's broadcast facility and a delay in paging throughput times results. This problem is compounded in paging services that offer national coverage to their subscribers. In such services a subscriber's pages are broadcast from several facilities, and therefore a delay in throughput times results at each facility.
The inventions disclosed in the Ser. No.: 08/379,425 and Ser. No.: 08/379,430 applications (the '425 and '430 applications, respectively), cited hereinabove, address many of the foregoing disadvantages of prior systems used to communicate with mobile individuals. Both of those inventions describe a call forwarding scheme in which each subscriber is assigned a Personal Telephone Number (PTN) and uses a two-way pager to forward calls placed to that number. In both cases, when a call is placed to the subscriber's PTN, a network database query is generated and information about how to handle the call is retrieved (referred to as "registration" type forwarding). In the '425 invention, the subscriber's pager number is retrieved from the database, the subscriber is paged, and the subscriber transmits a forwarding number back to the network via the two-way pager (referred to as "call-by-call" type forwarding). In the '430 invention, call forwarding may be carried out in the same way it is in the '425 invention, or, as an alternative, the forwarding number may be retrieved on the initial database query, thereby obviating the need to page the subscriber. The '425 and '430 inventions possess many advantages over prior call forwarding systems, and were therefore incorporated into the invention disclosed in application Ser. No. 08/579,539 (the '539 invention), which not only realized all of the advantages of the '425 and '430 inventions, but improved upon them by increasing the efficiency and flexibility of the call forwarding service offered.
One way in which the '539 invention improves upon the '425 and '430 inventions is by using the two-way pager to provide the bandwidth and protocol of the terminating station, which allows the network to allocate a communication channel for the forwarded call that is matched to the bandwidth and/or protocol of the terminating station, and to establish communications with the terminating station via the specified protocol.
Another way in which the '539 invention improves upon the '425 and '430 inventions is by incorporating the ability to perform secondary forwarding, revertive forwarding, and caller examination forwarding. Secondary forwarding refers to the forwarding of a call that has already been routed, or that has already received answer supervision. By incorporating secondary forwarding the burden on network resources may be reduced in that calls do not have to be held at a point in the network (or "parked") while they await forwarding, but rather routing may proceed as usual until a call forwarding signal is received, if such a signal is received at all. Furthermore, secondary forwarding provides additional call forwarding flexibility. For example, a subscriber may use the two-way pager to forward a call to a first terminating station where the call is answered, wait a period of time, and then use the two-way pager to forward the call to a second telephone station.
The revertive calling and caller examination procedures provide further flexibility by giving the subscriber two additional call forwarding procedures from which to choose. If the subscriber prefers to answer a call by initiating a revertive call from the desired terminating station, rather than by "picking up" the call at a predetermined terminating station, then the subscriber uses the two way pager to invoke the revertive calling procedure. If the subscriber wishes to have an incoming call automatically forwarded to a terminating station having a bandwidth and protocol corresponding to the bandwidth and protocol of the incoming call, then the subscriber uses the two way pager to invoke the caller examination procedure.
The invention of application Ser. No. 08/579,184 (the '184 invention) further enhances and improves the features and advantages of the '425, '430, and '539 inventions, by providing a call handling treatment for situations in which the subscriber is unable, or unwilling, to respond to a call-by-call alerting page. In such "subscriber unavailable" situations inadequate call treatment can waste network resources and result in the subscriber missing important calls. For example, consider a situation in which a subscriber goes to work and leaves her two-way pager at home. If the subscriber has specified call-by-call mode and a call is placed to the subscriber's PTN then the network will hold the call, page the subscriber, and await a response. A response, however, will not be provided since the subscriber is unavailable. One way to handle such a situation is to automatically forward the call to voice mail following a predetermined "time out" period.
Although a time out procedure provides a method for dealing with the subscriber unavailable problem, the procedure has drawbacks. One drawback of the time out procedure is that it requires that an unnecessary page be sent. If a subscriber could be recognized as unavailable prior to paging the subscriber, then the unnecessary page, and all the steps that go into generating that page, could be avoided, thereby freeing up the resources required to generate the page. Another drawback of the time out procedure is that there exists a possibility that a caller will not hold for the duration of the time out period, in which case the subscriber will "miss" the call.
The '184 invention overcomes these, and other, drawbacks by designing the two-way pager such that the paging service can determine whether the pager is on or off prior to sending a page. Such a determination may be made by the paging service alone or by the paging service in response to a request from the network, but whatever the case, the results of the determination may be stored by the paging service, by the network, or by some combination of the two. When it has been determined that the two-way pager of a call-by-call mode subscriber has been turned off, calls to that subscriber do not generate a page, but rather, they are forwarded to some predetermined forwarding number. In a preferred embodiment, the pager is equipped with an "automatic turn off", such as a body temperature sensor which turns the pager off when the pager is not being worn. Thus, a subscriber who is not wearing the pager, either inadvertently or deliberately, will not be paged in response to an incoming call and the call will be forwarded to a default number so that the subscriber does not "miss" the call. In any event, the network is apprised of a "pager off" status prior to generating a call-by-call alerting signal, thereby avoiding the allocation of network and/or paging service resources to the generation of a page that will not be received. Moreover, when the pager is equipped with the "automatic off" feature of the preferred embodiment, unnecessary pages and missed calls can be avoided in those situations where the subscriber is not carrying the pager but has neglected to turn the pager off.
Although such two-way paging systems apparently provide many advantages for mobile communication, they also are susceptible to deleterious effects from duplicate pages. A duplicate page may arise from various sources, including multi-path length transmission from a single paging station, and reception of a common page transmitted from more than one paging station. If the pager or mobile user does not or cannot recognize the second or subsequent page as being actually a duplicate or replica of a previously received page (i.e. the same page delayed in time), then any difference invoked by the subscriber between handling the original page and handling the duplicate page may result in inconvenience and confusion for both caller and subscriber, as well as in possibly a lost call. For instance, in response to an original page a subscriber may choose to forward the call to a first location having an answering machine. Then, upon receiving the duplicate page, the subscriber may choose to answer the page via a revertive call. Accordingly, since the original call has been, or is being routed, the network must "mid-stride" adjust to the alternative instruction for handling. These "mid-stride" adjustments by the network may also result in call routing errors even if the subscriber sends the same instruction for handling the original and duplicate pages. In addition, paging system and network system resources are wasted by handling of the signal transmitted from the subscriber to the paging service and network (referred to herein as a "reverse page") to specify call handling in response to a duplicate (i.e., not actual) page, and these resources are wasted even if the network disregards the second instruction.
Accordingly, in such two-way paging systems, it would be advantageous to prevent any return page from being sent by the mobile user in response to a duplicate page, or at least to minimize the impact of such duplicate pages on the paging service and network system resource allocation as well as on the network call handling itself. Such duplicate pages are also problems (e.g., inconvenience to subscriber) in conventional one-way paging systems; however, in such systems duplicate pages represent a less severe problem than for two-way paging systems because there are no reverse pages and concomitantly no provisions for call handling functions, such as call forwarding, in response to such reverse pages.
In any event, there is a need for an improved paging system which mitigates or eliminates duplicate pages, and this need is magnified by two-way paging systems.